The goals of this project are to determine where on the immunoglobulin molecule the idiotypic antigeic determinants measured in the previously described radioimmunoassay residue; to determine whether a human myeloma protein contains restricted allotypes and/or idiotypes which are shared with, and can be detected in the serum of, related individuals; and to assess the use of myeloma idiotype as a TSTA (Tumor Specific Transplantation Antigen) for following clinical course of multiple myeloma. No idiotype activity could be found in the sera of 47 other patients with IgA myeloma, nor could any be detected in the patient's parents or 4 siblings. The patient continues in clinical remission, but low idiotype levels are still detectable in his serum. Further characterization of the genetics of this patient's idiotype and restricted allotypes will be carried out by multiple specific absorptions on affinity chromatography columns. Attempts at in vitro specific tumor cell killing will be made. The RIA will continue to be used as a tool to follow the course of the patient's disease.